package com.wc.AlgoOJ_homework.AlgoOJ_test4.C_双端队列;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2024/3/15 19:28
 * @description http://43.138.190.70:8888/p/713?tid=65e5720827489dab814f4cab
 */
public class Main {
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static int N = 200010;
    static int[] a = new int[N];
    static int[] sub = new int[N];
    static int t, n, s;

    public static void main(String[] args) {
        t = sc.nextInt();
        while (t-- > 0) {
            Arrays.fill(a, -1);
            n = sc.nextInt();
            s = sc.nextInt();
            int sum = 0;
            for (int i = 1; i <= n; i++) {
                a[i] = sc.nextInt();
                sum += a[i];
            }
            if (sum < s) {
                out.println(-1);
                continue;
            }
            int[] dpr = new int[n + 10];
            for (int i = n; i >= 1; i--) {
                if (a[i] == 1) {
                    dpr[i] = i;
                } else {
                    dpr[i] = dpr[i + 1];
                }
            }
            for (int i = 1; i <= n; i++) {
                sub[i] = a[i] + sub[i - 1];
            }
            int l = 1;
            int r = n;
            while (r >= 1 && sub[r] - sub[l - 1] > s) {
                r--;
            }
            int res = n;
            while (r <= n && sub[r] - sub[l - 1] == s) {
                res = Math.min(res, l - 1 + n - r);
                l = dpr[l] + 1;
                if (dpr[r] == r) {
                    r = dpr[r] + 1;
                } else {
                    r = dpr[r];
                }
                while (r + 1 <= n && a[r + 1] == 0) {
                    r++;
                }
            }
            out.println(res);
        }
        out.flush();
    }
}

class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}